/***
 * Copyright 2002-2010 jamod development team
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ***/

package net.wimpi.modbus.io;

import java.io.DataOutput;
import java.io.IOException;
import java.io.InterruptedIOException;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.msg.ModbusMessage;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.net.UDPTerminal;

/**
 * Class that implements the Modbus UDP transport flavor.
 * 
 * @author Dieter Wimberger
 * @version 1.0 (29/04/2002)
 */
public class ModbusUDPTransport implements ModbusTransport {

	// instance attributes
	private UDPTerminal m_Terminal;
	private BytesOutputStream m_ByteOut;
	private BytesInputStream m_ByteIn;

	/**
	 * Constructs a new <tt>ModbusTransport</tt> instance, for a given
	 * <tt>UDPTerminal</tt>.
	 * <p>
	 * 
	 * @param terminal
	 *            the <tt>UDPTerminal</tt> used for message transport.
	 */
	public ModbusUDPTransport(UDPTerminal terminal) {
		m_Terminal = terminal;
		m_ByteOut = new BytesOutputStream(Modbus.MAX_IP_MESSAGE_LENGTH);
		m_ByteIn = new BytesInputStream(Modbus.MAX_IP_MESSAGE_LENGTH);
	}// constructor

	public void close() throws IOException {
		// ?
	}// close

	public void writeMessage(ModbusMessage msg) throws ModbusIOException {
		try {
			synchronized (m_ByteOut) {
				m_ByteOut.reset();
				msg.writeTo((DataOutput) m_ByteOut);
				m_Terminal.sendMessage(m_ByteOut.toByteArray());
			}
		} catch (Exception ex) {
			throw new ModbusIOException("I/O exception - failed to write.");
		}
	}// write

	public ModbusRequest readRequest() throws ModbusIOException {
		try {
			ModbusRequest req = null;
			synchronized (m_ByteIn) {
				m_ByteIn.reset(m_Terminal.receiveMessage());
				m_ByteIn.skip(7);
				int functionCode = m_ByteIn.readUnsignedByte();
				m_ByteIn.reset();
				req = ModbusRequest.createModbusRequest(functionCode);
				req.readFrom(m_ByteIn);
			}
			return req;
		} catch (Exception ex) {
			throw new ModbusIOException("I/O exception - failed to read.");
		}
	}// readRequest

	public ModbusResponse readResponse() throws ModbusIOException {

		try {
			ModbusResponse res = null;
			synchronized (m_ByteIn) {
				m_ByteIn.reset(m_Terminal.receiveMessage());
				m_ByteIn.skip(7);
				int functionCode = m_ByteIn.readUnsignedByte();
				m_ByteIn.reset();
				res = ModbusResponse.createModbusResponse(functionCode);
				res.readFrom(m_ByteIn);
			}
			return res;
		} catch (InterruptedIOException ioex) {
			throw new ModbusIOException("Socket timed out.");
		} catch (Exception ex) {
			ex.printStackTrace();
			throw new ModbusIOException("I/O exception - failed to read.");
		}
	}// readResponse

	public void flush() {
		m_ByteIn.skip(m_ByteIn.available());
	}

}// class ModbusUDPTransport
